Re: repeated failed open()'s results in lots of used memory [Was: [Fwd: memory consumption]]

[Andreas Dilger <adilger@turbolinux.com>]

You write:
> We've been experiencing a problem where an errant process would run in a 
> tight loop trying to create files in a directory where it did not have 
> access. While this errant process was running, we'd notice all of the 
> available memory shift from buffers/cache (or free) to used and stay 
> that way while the process was running. vmstat also reports heavy in/out 
> traffic on the swap, but swap consumption does not grow past a few dozen 
> megabytes. The memory used by the process itself does not grow.
> 
> Note that we increase the default values for certain FS parameters:
> 
> echo '16384' >/proc/sys/fs/super-max
> echo '32768' >/proc/sys/fs/file-max
> echo '65535' > /proc/sys/fs/inode-max

You are probably creating negative dentries.  Check /proc/slabinfo for
the number of dentries, and it will confirm this.  I'm not sure why
that would cause swapping, but then again I haven't checked the policy
for shrinking the dentry cache recently, and there have been a number
of changes in that area lately.

Cheers, Andreas
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert